Method of removing deposits of wax and like materials



METHOD OF REMOVING DEPOSITS F WAX AND LIKE MATERIALS Claude E. ZoBell, La Jolla, Calif., assignor to Texaco Development Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application June 9,

Serial No. 230,853

Claims. (Cl. 195-3) This invention relates to the dissolution and removal of waxes such as paraffin wax and like deposits from oil wells, pipe lines for conveying hydrocarbons, and similar locations where such waxes tend to collect and either halt or materially impede circulation.

This application is a continuation-in-part of my application Serial No. 21,307, filed April 15, 1948, now abandoned.

The deposition and collection of waxes such as parafiin wax in pipe lines, oil wells and the like has been a material problem in the petroleum industry. Such deposits are most always in inaccessible locations or in such forms as very small pore plugs, the latter being prevalent in oil wells. Consequently the deposits are both ditficult to reach and practically impossible to remove. While it is known that certain microorganisms will attack paraffin and effect its decomposition into readily removable products, such organisms are effective only under certain optimum conditions which are obviously impossible to secure and maintain in an oil well that may pass through strata of widely different compositions and temperatures or in a pipe line that may extend cross-country for many miles.

For this and other reasons, their use in pipe lines, oil wells, etc. has been considered impractical.

An object of this invention is to provide a novel process wherein such microorganisms or enzymes thereof can be efiiciently utilized in removing paraflin wax from pipe lines, oil wells and the like and inhibit further depositions of such wax therein.

Another object of the invention is the provision of a novel process for removing and inhibiting the formation of such parafiin deposits wherein the process, once initiated, is capable of continuing with a minimum of attention and little expense.

In its broader aspect, the present invention involves the simultaneous use of a number of different species of parafiin-consuming microorganisms or enzymes thereof, each species being capable'of consuming paraffin under diiferent conditions as to pH, temperature and other factors. More specifically, the invention involves the use of such microorganisms or enzymes thereof in combination with wax particles, such as flaked or granulated paraffin, whereby the ability of the microorganisms or enzymes thereof to adhere to the wax-coated surfaces of the pipe line or oil well is increased, the transplantation of the microorganisms being improved and the period of incubation, required for the microorganisms to manifest their wax-dissolving propensities, reduced. The invention contemplates the use of such microorganisms or their enzymes in the fluid being conveyed or otherwise handled, in the form of slugs or charges that may be fed periodically through a pipe line, or in the form of static charges to a pipe line when temporarily out of use.

As already stated, it is known that certain individual species of microorganisms and the enzymes thereof will assimilate paraflin wax. Typical of such microorganisms are species of Actinomyces, Nocardia, Mycobacterium,

2,742,398 Patented Apr. 17, 1956 Pseudomonas, Micromonospora, gillus, Penicillium, and Torula.

A number of such organisms are listed in the following table in the order in which they are considered most effective:

Nocardia (Proaczinomyces) parafiinae Nocardia corallina (Proactinomyces agrestis) Mycabacterium rubrum Mycobacterium hyalinum Aspergillus versicolor Aspergillus oryzae Aspergillus flavus Micrococcus parafiinae Bolrytz's cinerea All the microorganisms in the foregoing table, as well as other species of these genera, assimilate paratfin wax best in the presence of free oxygen. A good many, however, will utilize paraffin slowly in the absence of free oxygen in media which provide oxygen from such compounds as nitrates, nitrites, carbohydrates, alcohols, etc.

Other microorganisms which are facultative aerobes i. e. grow best in the presence of free oxygen but will grow in appropriate medium in the absence of free oxygen, include Nocaraia minima, Nocardia rubroperlincta and Nocardia veridis. Microaerophilic organisms, which require at least a trace of free oxygen for their growth, may also be used in the invention.

Examples of a microorganism capable of assimilating paraflin in the total absence of free oxygen are species of Desulfovibrio, Sporovibrio and other sulfate reducers. Desulfovibrio hydrocarbonoclasticus and Desulfovibrio halohydrocarbonoclasticus are typical species of Desulfovibrio. Another such microorganism is Nocardia salmonicolor. Such sulfate reducing bacteria are preferred because of absence of free oxygen which is the usual circumstance in a pipe line or oil well. Moreover, the various varieties thereof are active over a total temperature range from near 0 to C. and higher, although no one strain is active throughout this range. One strain may be limited to a maximum of 25 0.; another may exhibit maximum activity between 32 and 45 C. While the range of any one strain or variety may be narrow, a selected combination of the strains covers an exceedingly wide range. In addition, it is to be understood that most strains are susceptible to training or acclimatization'to different temperatures. The microorganism can also be acclimatized to environmental factors such as salinity and osmotic pressure.

Typical microorganism with their operating temperature range, the preferred range being shown in brackets, are listed below:

The temperature range is not the only factor to be con- (Proactz'nomyces agrestis) (22 to sidered in selecting or developing the cultures to be used.

Corynebacterium, Aspertheir ability to assimilate parafiin Wax in the aymahae ther environmental factors must also be considered inudingsalinity, oxygen tension," the typ'esmfhydrocar ons present, the possibilities of iron corrosion or biofoullg, the material from which the conduit or.well elements remade, etc. Obviously it Wouldnot bedesirablejto use it acid-producing strain in a concrete 'conduit'or anaerobic rains in the presence of free oxygen; All of the above re 'obvious'factors call'ing for cultureselections equally as bvious, such selections being well Within the skill of theiicrobiologist.

Assuming thatthe conditions. as to the above factors 1 a given pipe line are known and that a selection of trains has been made to meet those conditions, the strains re dispersed in a suitable nutrient medium,.usually-,ofthe. nineral salt type. As is well known to the art,,thecompoitions of such nutrients are selected in accordance with he requirements of the strain or strains used.

In the case of a pipe line, the inoculated medium may 1e charged directly into the line While the oil or other luid is being conveyed thereby. The microorganisms-are iistributedthroughout the line and brought into contact vim-the wax deposits. They function todissolve and effeet. the. removal of those deposits and tend to cling to :he walls of the pipe line in a manner to be readily available for any new deposits of wax.

Asa specific example of such a method, an inoculated microbiological nutrient medium can be prepared by inoculating a typical nutrient medium of the following composition with a number of differentvarieties of Desulfovibri0.. Sporovibrio and other sulfate reducers such as.- Desulfavibrio hydrocarbonoclasticus, Desulfovibrio halohydrocarbonoclasticus, varietiesthereof being selected as will be active over substantially the total temperature range to which the pipe line is subject. Other. microorganisms such as. Nocardia salmonicolor, Nocaridia minima.

Nocctrdia rubropertincta and Nocardia veridis may-also be added.

NaCl grarns 60' Ca(Cs'H503)z do 5.0' CaCOg- -do' 40.0 CaSoeZHzO do 50.0 KHzPOi do- 0.2 FeSOrJI-IzO' do 0.1 (NI-I4)2HPO4' do 051 Sea water ml 1000 In thetreatment of. a pipe line throu gh' which oil is being conveyed, the inoculated medium can be metered into the oilat the point of entry or .it.can bemetered into the line. at some intermediate point. medium may be as much'as from. 5 to of the oil, it beingunderstood that the mediumwill be diluted bythe oil.. By reason-of certain of thebacteria being thigmotactic whereby they fix' themselves to the internal surface of.

the pipe line ashcreinafter. explained, the dilution proborganisms or their:enzymes..-is reduced.v Hence: it is' -preferred to charge theinoculated medium as an entity into: theLpipeline between charges of the fluidbeing conveyed thereby. The medium then. moves .as a substantially solid slug through the line, the microorganismsbeing brought into contact with the paraflirt deposits.

In this method of treatment, theollfed into thepipeline is interrupted, and inoculated medium of "the above-described type. is/chargedinto ,thezline in a quantitytofill 100. to .200 feet of. the linez. The,feed .of oilqis resumed The quantity of inoculated When the well isbeing 1 whereupon the inoculated medium moves as a substantial- 15 solid slug "through the line, the thigrnotactic' bacteria adhereing to the surface thereof. At some convenient valving point along the line or at the terminus thereof, the flow of oil from the line is shut off and the slug of medium diverted and removed from, the line. The approach of the slug to such a valving point or terminus can easily be determined by charging :the slug with a-small amount of a radioactive substance whereby the approach of the slugand its passage at any point can bedetermined by a Geiger-Mueller detector or. the equivalent outside the-pipe line. A second preferred method maybe used whenit-i-s possible toshut otfthe pipe linetemporarily or the pipe line is in intermittent use; In this case, the inoculated medium is charged to the empty line as between two valve controlled points and-'pcrmit-tedto remain therein until it is desired to put the line in use again. The charge is then withdrawn and stored for use again since it is capable. ordinarily of. such reuse. If necessary, the nutrient constituents maybe replenished and fresh cultures added.

To illustrate this particular method, Nocardia (Pro nctz'nomyces) parayffinnae, Nocardia corallina (Proa'cIF nomyces agrestis'), Mycobacterium rubrum, Mycobacterium hyalinum; Aspergillus oryzae, M icrococcus paraffinae and Botrytis cinerea are charged to a nutrient medium of the following composition, the bacteria selected being of types'th'atwillb'e effective over the temperature'range encountered.

The addition of certain ions such as copper, mercury, zinc, bismuth, and iodine to the medium in trace amounts may stimulatethe activity of the microorganisms.

Assuming the pipe line is shut off and substantially drained between two valved points, the inoculated medium is charged 'to the empty section in a volume to substantially fill the sectionand air or any oxygen-containing medi-' um-passed through the line from one shut-oif point to the other: This'is continued as long as is necessary to-clean" the line or as long, as the line can be held inactive as respects the transport of oil. The inoculated medium is then'withdrawn and stored for reuse or discarded-as de'' sired. Since some of'the' bacteria such' as Proactinomycesparajfinae' are thigmotactic, they will be usually retained quantity to continue their Inc-- in the line in substantial tab'olism;

Similarmethods can be practiced in the cleaning of -oil wells; the medium being charged to the well and with-- Orthe well may be charged with themedium' and closed until the-well is cleaned. In the case of wells being-dug; the medium may be mixed with the drawnwith theoil.

drilling 'mud and distributed throughout the well.

So-called attachment or stalked bacteria, more-recently-termed thigmotactic bacteria are preferred be cause of -theinability to attach and fix' themselves to sur-- faces such'as' the interior. surfacesof .a pipe. line, oil tank oroillwell'. Desulfovibrio hydrocarbonoclasticus is type ical of ."such' an anaerobe and Proactinomyces parafiinae of suchan aerobe.

The -,term.- microorganism? as used herein is :intended.

to include bacteria'andtheir enzymes as well as fungi;

able ofperforatingand dissolving paraffin wax.

at-ing parafiin Wax to a depth of /2 inch or rnore. Such fungi are capable of use only in,the presence-offrees oxygen.

In H1OS['ii'lSIaIlCS,' lt is preferred to charge them.

oculated medium with fine wax particles such as flaked or granulated paraffin, although the procedures outlined in the foregoing examples are satisfactory. Such particles are sufliciently fine to stay in suspension in the nutrient medium and function as mechanical carriers for the microorganisms. By reason of their waxy nature, they tend to cohere to the wax deposits in the pipe line or oil well, thus bettering the transplantation of the organism and shortening the incubation period.

It is to be understood that in some cases as in a short section of a pipe line or in some oil wells, the environment may remain substantially constant and be suited to one particular species or variety of wax-consuming microorganism. In such case, it may be necessary to use only single species or variety rather than a plurality thereof.

From the above, it is believed evident that the present process provides a simple and inexpensive method of removing wax from locations hitherto considered in accessible. Such locations are found in pipe lines, oil wells, storage tanks and other places. By reason of the tendency of the microorganisms, particularly when associated with parafiin in small particles or when thigmotactic varieties are used, to adhere to the interior surfaces of the pipe lines and other locations, the process continues to be effective in inhibiting further deposits of paraflin.

While reference has been made herein specifically to a wax such as paraflin wax, it is to be understood that the invention is applicable to deposits of any material susceptible to attack by microorganisms.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A method of dissolving, removing, and inhibiting deposition of wax and like materials in pipe lines for hydrocarbons, oil wells and similar locations comprising the step of intermittently contacting said wax deposits with a microbiological nutrient medium having relatively fine particles of Wax suspended therein and inoculated with a plurality of difierent species of wax-consuming microorganisms, each species being selected in accordance with its environmental characteristics so that one or more species is effective on said wax deposits throughout substantially the entire range of changes in environmental characteristics in said locations.

2. A method of dissolving, removing and inhibiting deposition of wax and like materials in pipe lines for hydrocarbons wherein there is normally a continuous flow of fluid therethrough comprising the steps of intermittently substituting a charge of a microbiologcial nutrient medium for said fluid, said medium having relatively fine particles of wax suspended therein and inoculated with a plurality of different species of wax-consuming microorganisms, each species being selected in accordance with its environmental characteristics so that one or more species is elfective on said wax throughout substantially the entire range of changes in environmental characteristics in said locations.

3. A method of dissolving, removing, and inhibiting deposition of wax and like materials in a pipe line for hydrocarbons comprising the steps of periodically discharging said line of hydrocarbons, charging said line with microbiological nutrient medium having relatively fine particles of wax suspended therein and inoculated with a plurality of different species of wax-consuming microorganisms, each species being selected in accordance with its environmental characteristics so that one or more species is effective on said wax throughout substantially the entire range of charges in environmental characteristics in said line, discharging said nutrient medium, and recharging said line with hydrocarbons.

4. A method of dissolving, removing, and inhibiting deposition of wax and like materials in pipe lines for hydrocarbons, oil wells and similar locations comprising the step of intermittently contacting said wax deposits with a microbiological nutrient medium inoculated with a plurality of difierent species of wax-consuming microorgan-v isms, at least one of which is Proactinomyces paraflinae, a thigmotactic microorganism, each species being selected in accordance with its environmental characteristics so that one or more species is effective on said wax deposits throughout substantially the entire range of changes in environmental characteristics in said locations.

5. A method of dissolving, removing and inhibiting deposition of wax and like materials in pipe lines for hydrocarbons wherein there is normally a continuous flow of fluid therethrough comprising the steps of intermittently substituting a charge of a microbiological nutrient medium for said fluid, said medium being inoculated with a plurality of ditferent species of wax-consuming microorganisms, at least one of which is Proactinomyces parafi'inae, a thigmotactic microorganism, each species being selected in accordance with its environmental characteristics so that one or more species is effective on the wax deposits throughout substantially the entire range of changes in environmental characteristics in said 10- cations.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF DISSOLVING, REMOVING, AND INHIBITING DEPOSITION OF WAX AND LIKE MATERIAL IN PIPE LINES FOR HYDROCARBONS, OIL WELLS AND LIKE SIMILAR LOCATIONS COMPRISING THE STEP OF INTERMITTENTLY CONTACTING SAID WAX DEPOSITS WITH A MICROBIOLOGICAL NUTRIENT MEDIUM HAVING RELATIVELY FINE PARTICLES OF WAX SUSPENDED THEREIN AND INOCULATED WITH A PLURALTITY OF DIFFERENT SPECIES OF WAX-CONSIMING MICROORGANISMS, EACH SPECIES BEING SELECTED IN ACCORDANCE WITH ITS ENVIRONMENTAL CHARACTERISTICS SO THAT ONE OR MORE SPECIES IS EFFETIVE ON SAID WAX DEPOSITS THROUGHOUT SUBSTANTIALLY THE ENTIRE RANGE OF CHANGES IN ENVIRONMENTAL CHARACTERISTICS IN SAID LOCATIONS. 